1. Field of the Invention
The present invention relates to an apparatus for fabricating a semiconductor device such as an integrated circuit, a liquid crystal display, a solar cell or the like, particularly to a plasma processing apparatus.
2. Description of the Background Art
In recent years, a diode parallel plate plasma enhanced CVD system having electrodes arranged in parallel is employed in the method of forming a thin film on a substrate. Using the diode parallel plate plasma enhanced CVD system, gas is excited and disintegrated by the plasma potential due to the presence of the plasma 2-5 cm above the surface of the substrate. The disintegrated gas reacts with the surface of the substrate, whereby the surface of the substrate is damaged or contaminated.
Japanese Patent Laying-Open No. 8-279498 discloses a plasma processing apparatus having plasma located remote from the substrate as a method of solving the aforementioned problem. This plasma processing apparatus is shown in FIG. 6.
Referring to FIG. 6, the plasma processing apparatus has a substrate 8 to be processed mounted on a substrate holder 7 to be shifted in the direction of arrow A below a plasma chamber 1 by a substrate transport unit 10. A substrate heater 9 is arranged under substrate transport unit 10.
An electric field generator 21 formed of a high frequency power supply 3 and a resonator 4 is arranged outside plasma chamber 1. The high frequency generated by high frequency power supply 3 is guided into plasma chamber 1 through a dielectric window 6 to produce an electric field by resonator 4.
An excitation gas introduction nozzle 15 is provided at the upper region in plasma chamber 1 to introduce excitation gas. A reaction gas introduction nozzle 16 is arranged at the lower region in plasma chamber 1 to introduce reaction gas. The excitation gas input through excitation gas introduction nozzle 15 is converted into plasma and mixed with the reaction gas input through reaction gas introduction nozzle 16. The mixture is discharged from a plasma chamber opening 35 so as to effect gas-phase reaction at the surface of substrate 8.
Plasma chamber 1 is functionally divided into a plasma region 30 and a drift region 31. Plasma region 30 includes a radioactive species volume 34 including plasma 32 in which activated species are generated and an afterglow 33 in which collapsing radioactive activated species move.
Drift region 31 is located between radioactive species volume 34 and plasma chamber opening 35 where non-radioactive activated species move. Drift region 31 serves to filter and remove activated species that are not selected to promote collision of extremely dynamic activated species, whereby damage onto the surface of substrate 8 is suppressed. Drift region 31 includes an excitation gas flow to reduce reaction gas flowing backwards towards plasma 32.
In FIG. 6, a process chamber 2 is provided below plasma chamber 1. A shield plate 5 is arranged outside plasma chamber 1. Substrate 8 is introduced into plasma chamber 2 through a gate valve 11 and output from process chamber 2. An evacuation outlet 13 is arranged at the upper wall of process chamber 2.
In the plasma processing apparatus of the above-described structure, the volume of radioactive species volume 34 including plasma 32 and afterglow 33 changes depending upon the processing condition such as the process pressure or high frequency output. The change in volume of radioactive species volume 34 corresponding to different process pressure is shown in FIGS. 7A-7C.
FIG. 7C corresponds to the case where the process pressure is lower than that of FIG. 7B. It is appreciated from FIG. 7C that radioactive species volume 34 is increased so that afterglow 33 reaches the neighborhood of reaction gas introduction nozzle 16 to induce the possibility of the reaction gas being converted into plasma when the process pressure is low. This means that the surface of substrate 8 may be damaged or contaminated despite the improved processing rate.
FIG. 7A corresponds to the case where the process pressure is higher than that of FIG. 7B. It is appreciated from FIG. 7A that radioactive species volume 34 becomes smaller when the process pressure is high. Occurrence of damage or contamination at the surface of substrate 8 is reduced whereas the processing rate is degraded.
The volume of radioactive species volume 34 changes corresponding to difference in the high frequency output, so that similar problems are encountered.
Thus, the volume of radioactive species volume 34 changes depending upon the processing condition, so that the degree of damage or contamination on the surface of substrate 8 and the processing rate differ. The system is subject to two competing considerations which represent the relationship of tradeoff.
In view of the foregoing, an object of the present invention is to provide a plasma processing apparatus that allows processing of high quality under a processing condition of a wider range by setting the distance between the plasma region and the substrate in optimum even when the processing condition such as the process pressure or high frequency output differs.
According to an aspect of the present invention, a plasma processing apparatus includes a plasma chamber having a plasma region to generate plasma, a process chamber arranged below the plasma chamber and having a region where a plasma process is applied on a substrate to be processed, and a distance variable mechanism rendering the distance between the plasma region and the substrate to be processed variable.
In the foregoing plasma processing apparatus, the distance variable mechanism preferably includes a jack mechanism fixed to the plasma chamber and the process chamber. In this case, it is further preferable for the distance variable mechanism to include a motor connected to the jack mechanism. The jack mechanism is preferably connected to the motor through a gear and a rod.
According to another aspect of the present invention, a plasma processing apparatus includes a plasma chamber having a plasma region to generate plasma, a process chamber arranged below the plasma chamber and having a region to apply a plasma process on a substrate to be processed, and a plasma chamber expansion/contraction mechanism to expand or contract the length of the plasma chamber.
In the above plasma processing apparatus, the plasma chamber expansion/contraction mechanism preferably includes a bellows to provide flexible connection between the plasma chamber and the process chamber.
In the above plasma processing apparatus, the plasma chamber preferably includes a first plasma chamber connected to the process chamber and a second plasma chamber connected to the first plasma chamber. The plasma chamber expansion/contraction mechanism preferably includes a bellows providing flexible connection between the first and second plasma chambers. In this case, the plasma chamber expansion/contraction mechanism preferably includes a bellows providing flexible connection between the first plasma chamber and the process chamber. In this case, it is preferable for the second plasma chamber to include a window to introduce a high frequency electric field therein.
It is preferable for the plasma processing apparatus to further include a partition member between the plasma chamber expansion/contraction mechanism and the plasma region.
According to a further aspect of the present invention, a plasma processing apparatus includes a plasma chamber having a plasma region to generate plasma, a process chamber arranged below the plasma chamber and having a region to apply a plasma process on a substrate to be processed, an excitation gas introduction nozzle to introduce into the plasma chamber excitation gas to generate plasma, a reaction gas introduction nozzle to introduce in the process chamber reaction gas to apply a plasma process on the substrate to be processed, and a nozzle distance variable mechanism rendering the distance between the excitation gas introduction nozzle and the reaction gas introduction nozzle variable.
In the above plasma processing apparatus, the plasma chamber preferably includes a first plasma chamber connected to the process chamber and a second plasma chamber connected to the first plasma chamber. The excitation gas introduction nozzle is provided at the second plasma chamber. The reaction gas introduction nozzle is provided at the first plasma chamber. The nozzle distance variable mechanism preferably includes a jack mechanism fixed to the first plasma chamber and the second plasma chamber. In this case, the nozzle distance variable mechanism preferably includes a motor connected to the jack mechanism. The jack mechanism is preferably connected to a motor through a gear and a rod.
In the above plasma processing apparatus, the nozzle distance variable mechanism preferably renders the distance between the plasma region and the substrate to be processed variable.
Since the distance between the plasma region and the surface of the substrate to be processed can be set variable by the plasma processing apparatus of the present invention, the distance between the plasma region and the surface of the substrate to be processed can be set in optimum according to the processing condition. Damage on the surface of the substrate to be processed can be prevented by optimizing the drift region. Therefore, a plasma process of high quality is allowed under a wide range of processing condition.
The distance between the plasma region and the surface of the substrate to be processed can be set in optimum according to the processing condition by expanding or contracting the plasma chamber. Damage onto the surface of the substrate to be processed can be prevented by optimizing the drift region. Therefore, a plasma process of high quality is allowed under a wide range of processing condition.
By rendering variable the distance between the excitation gas introduction nozzle and the reaction gas introduction nozzle, only the effective activated species can be coupled with the reaction gas without coverage of the reaction gas introduction nozzle with the radioactive species volume. A plasma process can be carried out always in stability.
By rendering variable the distance between the plasma region and the surface of the substrate to be processed and also the distance between the excitation gas introduction nozzle and the reaction gas introduction nozzle, the distance between the plasma region and the surface of the substrate to be processed can be optimized according to the processing condition. Damage onto the surface of the substrate to be processed can be prevented by optimizing the drift region. A plasma process of high quality is allowed under a wide range of processing condition. Only the effective activated species can be coupled with the reaction gas without coverage of the reaction gas introduction nozzle with the radioactive species volume. A plasma process can be carried out always in stability.
By providing a partition wall between the plasma expansion/contraction mechanism and the plasma region, damage and product adherence caused by the plasma towards the mechanism can be prevented. Also, the scatter of dust particles from the mechanism can be prevented.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.